Data transmission paths of the generic type are known. They are used for the purpose of detecting whether data transmitted by a sender has reached the receiver in unmodified form. For this, check sum methods are known, for example, in which a check sum for the data to be transmitted is determined on the sender side and attached to the data to be transmitted. The check sum of the transmitted data is subsequently determined on the receiver side and compared to the attached transmitted check sum. If this check is positive, i.e., a correct transmission of the data from sender to receiver is detected, the integrity of the data is ensured and the data may be further processed on the receiver side. If the check shows a negative result, i.e., a modification of the data on the sender-receiver path has been detected, a procedure for correcting the transmission error is initiated.
In particular in safety-relevant and time-critical applications, e.g., when activating the brake system of a motor vehicle, the check of the data integrity must meet high demands. In addition to the manual request by the motor vehicle user, a brake request may also be triggered today by safety functions such as an anti-lock braking system, an electronic stability program, or a brake assistant, or by comfort functions such as an adaptive cruise control. The signals are transmitted in part by the CAN (Controller Area Network) vehicle communication network; additional control units, for the dashboard, the engine, or a diagnostic system, for example, may also be connected to the CAN. Since unauthorized actuation of a brake system, in particular the execution of automated full braking, presents a significant danger for the motor vehicle user and other road users, a brake may only be actuated when the control unit of the brake system has actually generated a brake request. Unauthorized brake requests may be caused, for example, by errors in control units connected to the CAN or by interferences within the CAN itself. An aggravating fact is that such applications are time-critical, i.e., the time period between the brake request by the control unit of the brake system and the required brake actuation is so small that no time remains for verifying the validity of the brake request, either through the control unit or the brake itself. In terms of time, it is frequently possible to transmit only a single actuation signal. No time remains for correcting an erroneous signal by another signal, or for awaiting another signal for a check. Therefore, a single signal takes on great importance with an irreversible character to a certain extent.